Effective multi-step Ge condensation process using intermittent SiO2 strip to obtain a high-Ge concentration and a thick Ge-on-insulator (GeOI) substrate for p-MOSFET

Abstract

The effect of an intermittent SiO2 strip process in multi-step oxidation on the physical properties of a condensed Ge-on-insulator (GeOI) layer was investigated to realize a higher Ge concentration. By utilizing an intermittent SiO2 strip during the condensation process, we demonstrated a 21-nm GeOI layer with a Ge concentration of higher than 95 at% and confirmed that total process time to reach a Ge concentration higher than 95 at% could be reduced by maximum of 77% compared to a conventional process without the SiO2 strip. This was attributed to the intermittent SiO2 strip process causing Ge atoms to be volatized in the O-2 environment during the condensation process. The intermittent SiO2 strip is essential to achieve a Ge concentration higher than 95 at% and is very effective in realizing a high Ge concentration and a thick Ge-on-insulator substrate.